Hello.
Please refrain from posting threads like this in News section.
As for your question, exp only contributes to your other ninjas, not your line-up.
so for example, if your main is currently lvl 76, and your 3 other ninjas are lvl 75 (with 99.9% exp), if you battle those ninjas in the map, your 3 other ninjas will earn the exp, but not your main.